(1) Field of the Invention
This invention relates to injection molding techniques and apparatus and more particularly to mold arrangements utilized with the encapsulation of electrical components.
(2) Prior Art
It is common to mold insulation on one or more circuit elements having leads or terminals connected thereto by potting or pouring fluid insulation around the elements held in a pot like receptacle which may form a part of the finished product. The operation is slow and it does not generate a strong bond between the elements and the insulation. Injection molding with a thermoplastic material is superior because of improved sealing action, curing time and fast injection capabilities. High pressures utilized to force the thermoplastic material into a mold and around the components disarrange the electrical components with respect to one another and with respect to the mold walls. This affects the heat transfer characteristics of electrical components, and hence diminishes their efficiency and life expectancy.
Early attempts at encasing electrical components are shown in U.S. Pat. No. 2,713,700 to Fisher and 2,856,639 to Forrest et al. The patent to Fisher suggests enclosing the component body within a protective plastic medium whose molding requires no injuriously high pressures, and supported between opposed mold sections. The patent to Forrest et al shows a method of encasing electrical coils by means which includes mounting them on a mandrel within a mold and pouring the encapsulant into the mold. A further attempt at encasing articles is shown in U.S. Pat. No. 2,747,230 to Magrues wherein the article is placed between halves of a preliminary plastic form which is then enclosed in a mold and lugs in the form hold the article in the desired position. The form encloses the article and protects it from the encapsulant material, the form coalescing with the encapsulant, the article however not being closely supported by the encapsulant.
Advances in the insulating and encapsulating of components are shown in U.S. Pat. No. 3,044,127 to Alden, which discloses a method of fitting a separate support in a mold, placing an electrical element on the support to securely position the element in the mold, closing the mold, injecting insulation into the mold at least partially to encase the element, and subsequently separating the enclosed element and support from the mold. The support may be molded on a part of the element prior to secondary encasement, or the primary covering may be formed separately and applied to the element prior to putting it in the mold for secondary encasement. However, the invention disclosed in the U.S. Pat. No. 3,044,127 patent to John Alden is not applicable to an entire circuit and to the problems of alignment between the elements, internal flow problems of the thermoplastic material therearound, circuit inter-fitting and circuit support within the carrier.
It is thus an object of the present invention to provide a method of encapsulating an electrical circuit comprising a plurality of discrete however-interconnected electrical components.
It is another object of the present invention to provide a carrier for an electrical circuit that may be encapsulated with the electrical circuit.
It is yet another object of the present invention to provide a carrier for an electronic circuit which permits simple error free loading thereof, while maintaining alignment of the electrical components therein during encapsulation.
It is a further object of the present invention to provide a method for encapsulating an electronic circuit wherein the circuit can be loaded in a carrier in a simple manner prior to encapsulation, said carrier deforming to secure and maintain the electronic components therein in aligned positions.